Cold workable and age-hardenable steel

ABSTRACT

A cold workable and age-hardenable steel includes weight percentages of carbon and manganese within an area enclosed by a line connecting points P, Q, R and S as shown in the accompanying FIG. 1; less than 0.6 weight % of silicon; as age-hardenability improving alloying metals more than 2.5 weight % of nickel and more than 0.6 weight % of aluminum or more than 2.5 weight % of nickel, more than 0.6 weight % of aluminum and more than 0.5 weight % of copper or more than 2.5 weight % of nickel, more than 0.6 weight % of aluminum and more than 0.5 weight % of titanium or more than 2.5 weight % of nickel, more than 0.6 weight % of aluminum, more than 0.5 weight % of copper and more than 0.5 weight % of titanium; the total amount of nickel and aluminum or nickel, aluminum and copper or nickel, aluminum and titanium or nickel, aluminum, copper and titanium being in the range of from 4.5 to 6.5 weight %; and the balance which is substantially iron and impurities. Ductility, temperability and machinability improving elements may be added as well as metals for improving the fineness of the crystalline particles of the steel.

Asada et a1.

[451 Dec. 16, 1975 COLD WORKABLE AND AGE-HARDENABLE STEEL [75]Inventors: Chiaki Asada, Nagoya; Toshiyuki Watanabe, Nishio, both ofJapan [73] Assignee: Daido Seiko Kabushiki Kaisha,

[22] Filed:

Nagoya, Japan May 2, 1974 [21] Appl. No.: 466,512

Related US. Application Data [62] Division of Ser. No. 187,825, Oct. 8,1971, Pat. No.

[30] Foreign Application Priority Data Oct. 19, 1970 [52] U.S.Cl.....[51] Int. Cl.

Japan 45-91150 75/124; 75/125 C22C 38/06; C22C 38/16 WEIGHT OF MANGANESE5(C,Mn:0%) 0.05

Primary ExaminerL. Dewayne Rutledge Assistant Examiner-Arthur J. SteinerAttorney, Agent, or FirmWenderoth, Lind & Ponack [57] ABSTRACT A coldworkable and age-hardenable steel includes weight percentages of carbonand manganese within an area enclosed by a line connecting points P, Q,R and S as shown in the accompanying FIG. 1; less than 0.6 weight ofsilicon; as age-hardenability improving alloying metals more than 2.5weight of nickel and more than 0.6 weight of aluminum or more than 2.5weight of nickel, more than 0.6 weight of aluminum and more than 0.5weight of copper or more than 2.5 weight of nickel, more than 0.6 weightof aluminum and more than 0.5 weight of titanium or more than 2.5 weightof nickel, more than 0.6 weight of aluminum, more than 0.5 weight ofcopper and more than 0.5 weight of titanium; the total amount of nickeland aluminum or nickel, aluminum and copper or nickel, aluminum andtitanium or nickel, aluminum, copper and titanium being in the range offrom 4.5 to 6.5 weight and the balance which is substantially iron andimpurities. Ductility, temperability and machinabili'ty improvingelements may be added as well as metals for improving the fineness ofthe crystalline particles of the steel.

5 Claims, 3 Drawing Figures P(C 0%, Mn 1.80%)

Q (CI0.080%, MnIO.50%)

(CI0.08%,MnZO%) WEIGHT OF CARBON US. Patent Dec. 16, 1975 WEIGHT "/6 OFMANGANESE FIG. I

P(C Z 0%, Mn 1 1.80%)

WEIGHT OF CARBON VICKERS HARDNESS U.S. Patent Dec. 16, 1975 Sheet2of23,926,621

1200- FIG. 2

U) I (D LU z 800- Q (I 1 I GOO UJ X 2 E 2 u I 400- o o'.1 012 0'3 0:4ofs DEPTH MEASURED FROM THE SURFACE OF THE STEEL (mm) FIG. 3

0.62 0'04 0:06 o os d1 J 0.2 0.3 0.4 0.5 CENTER DEPTH MEASURED FROM THESURFACE OF THE STEELS (mm) COLD WORKABLE AND AGE-HARDENABLE STEEL Thisis a division, of application Ser. No. 187,825, filed Oct. 8, 1971, nowUS. Pat. No. 3,856,514.

- DETAILED EXPLANATION OF INVENTION This invention relates to coldworkable and age-hardenable Ni-Al type, Ni-Al-Cu type, Ni-Al-Ti type andNi-Al-Cu-Ti type steels which are machinable with easiness and have highductility under the solution treatments.

Business machines such as data-processing machines and complicatedarticles such as racks, gears, arms, stoppers and carriages used inmaking a computer are made by using a case hardening steel and then theyare heat-treated for hardening the case hardening steel. Also suchbusiness machines and such complicated articles are made of aheat-treated band steel. In such a case, the case hardening steel has adefect so that it has strain after it was heated-treated, and also theheattreated band steel has a defect so that it is difficult to work itinto such a complicated article. i It is preferable to use anage-hardenable steel, which has less strain after it was heat-treated,for making such a business machine and such a complicated article butthe prior known age-hardenable steels do not always give thesatisfactory results in making the business machines and the complicatedarticles.

The inventors have investigated for removing the above mentioned defectsfrom the prior known steels and have discovered cold workable andage-hardenable steels which are improved in their cold-workability byreducing their hardness under the solution treatments and can behardened by age-treatment and have little strain after they wereheat-treated.

It is an object of this invention to provide a cold workable andage-hardenable steel consisting essentially of weight percentages ofcarbon and manganese within an area enclosed by a line connecting pointsP, Q and R to a point S as shown in the accompanying FIG. 1; less than0.6 weight of silicon; as age-hardenability improving alloying metalsmore than 2.5 weight of nickel and more than 0.6 weight of aluminum ormore than 2.5 weight of nickel, more than 0.6% of aluminum and more than0.5 weight of copper or more than 2.5 weight of nickel, more than 0.6weight of aluminum and more than 0.5 weight of titanium or more than 2.5weight of nickel, more than 0.6 weight of aluminum, more than 0.5 weightof copper and more than 0.5 weight of titanium; the total amount ofnickel and aluminum or nickel, aluminum and copper or nickel, aluminumand titanium or nickel, aluminum, copper and titanium being in the rangeof from 4.5 to 6.5 weight and the balance which is substantially ironand impurities, said point P indicating zero weight of carbon and 1.8weight of manganese, said point Q indicating 0.08 weight of carbon and0.5 weight of manganese, said point R indicating 0.08 weight of carbonand zero weight of manganese and said point S indicating zero weight ofcarbon and zero weight of manganese.

Also, it is another object of this invention to provide a cold workableand age-hardenable steel consisting essentially of weight percentages ofcarbon and manganese within an area enclosed by a line connecting pointsP, Q and R to a point S as shown in the accompanying FIG. 1; less than0.6 weight of silicon; as agehardenability improving alloying metalsmore than 2.5 weight of nickel and more than 0.6 weight of aluminum ormore than 2.5 weight of nickel, more than 0.6 weight of aluminum andmore than 0.5 weight of copper or more than 2.5 weight of nickel, morethan 0.6 weight of aluminum and more than 0.5 weight of titanium or morethan 2.5 weight of nickel, more than 0.6 weight of aluminum, more than0.5 weight of copper and more than 0.5 weight of titanium; the totalamount of nickel and aluminum or nickel, aluminum and copper or nickel,aluminum and titanium or nickel, aluminum, copper and titanium being inthe range of from 4.5 to 6.5 weight and the balance which issubstantially iron and impurities in combination with at least one ofductility and temperability improving alloying metals alone or at leastone of alloying metals alone for improving the fineness of thecrystalline particles of said steel and at least one of machinabilityimproving alloying metals alone or in combination with at least twometals selected from said ductility and temperability improving alloyingmetal, said alloying metal for improving the fineness of the crystallineparticles of said steel and said machinability improving alloying metal,said point P indicating zero weight of carbon and 1.8 weight ofmanganese, said point Q indicating 0.08 weight of carbon and 0.5 weightof manganese, said point R indicating 0.08 weight of carbon and zeroweight of manganese and said point S indicating zero weight of carbonand zero weight of manganese.

The'reasons why carbon, manganese, silicon, agehardenability improvingalloying metals, ductility and temperability improving alloying metals,alloying metals for improving the fineness of the crystalline particlesof the steel and machinability improving alloying metals are defined asthe components and also in their amounts in accordance with thisinvention are explained hereinafter.

1. Carbon and Manganese: I

The'cold workability which is determined 'on the basis of thetight-bending of the steel is varied depending upon not only thesolution treated hardness but the contents of carbon and manganese, andtherefore it is preferable to use carbon and manganese in the amounts asdefined within the area enclosed by the line connecting the points P, Qand R to the point S as shown in the accompanying FIG. 1 showing carbonversus manganese. This is fully explained as the description goes on.

2. Silicon:

A small amount of silicon is essential for conducting the smeltingtechnique but a larger amount of silicon impairs the ductility and thecold workability of steels and therefore the content of silicon isdefined to less than 0.6 weight percentage.

3. Nickel:

Nickel is an alloying element for producing a Ni-Al alloy or a Ni-Tialloy, and also it is an essential alloying element for improving theage-hardenability of steels by the synergistic actions and effectsbetween Ni and Cu but the actions and effects of Ni are not remarkablewhen it is added into steels in an amount of below 2.5 weightpercentages.

4. Aluminum:

Aluminum is an alloying element for producing an Al=Ni alloy and anAl-Ti alloy, and also it is an essential all ying element for improvingthe age-hardenability of steels by the synergistic actions and effectsbetween A1 and Cu, and therefore it is required to use aluminum in anamount of above 0.6 weight percentage.

5. Copper: I

Copper is deposited as an e-phase in steels for improving theage-hardenability of the steels and it is used as an essential elementfor strengthening the steels by the synergistic actions and effectsbetween Cu and depositions resulted by the presence of nickel, aluminumand titanium. It is preferable to use copper in an amount of above 0.5weight percentage.

6. Titanium:

Titanium is an alloying element for producing a metal compound betweenTi and Ni or Ti and Al and it is cobalt and less than 0.5 weight ofberyllium are incorporated with said steel but they impede the coldworkability of the steel and become expensive when they are used in alarger amount. Also, the cold workable and age-hardenable steel of thisinvention is improved markedly in its temperability when a small amountof boron is incorporated with said steel but the ductility and theoutput of the steel are impeded when boron is incorporated with thesteel in an excess amount. Therefore, it is preferable to use boron inan amount of below 0.01 weight percentage.

8. Niobium, tantalum, vanadium and zirconium:

These metals can be used for improving the cold workability under theconditions of solution treatment used as an essential element forimproving the age-harand the fineness of the crystalline particles ofthe cold denablllty of steels by the synergistic actions and efworkableand age-hardenable steel of this invention but fects between Ti and Cu.It is preferable to use titanium they become expensive and the output ofthe steel is in an amount of above 0.5 weight percentage. impeded whenthey are used in a larger amount. Therelt 1s ObVlOUS from the data asshown in Table 2 that fore, the total amount of niobium and tantalum isdethe total amount of the age-hardenability improving fined to less than0.5 weight percentage and vanadium alloying metals which are added inthe cold workable and zirconium are defined to less than 0.5 weightperand age-hardenable steel of this invention in combinacentagerespectively. tion of Ni and Al or Ni, Al and Cu or Ni, Al and Ti or 9.Sulphur, lead, selenium, tellurium and bismuth: N1, Al, Cu and Ti isrequired to limit to the lower con- These metals can be used forimproving the machintent of 4.5 weight percentages for obtaining theinability and retaining the age-hardenability of the cold tended Vickersage-hardness of above 300. However, workable and age-hardenable steel ofthis invention but if the age-hardenability improving alloying metalsare the steel is impeded in its ductility and workability and used in alarger amount of above 6.5 weight percentit tends to become brittle whensuch metals are incorages, they become expensive and also in some casesporated with the steel in a larger amount. Therefore it aluminum, copperand titanium impede the output of is preferable to use sulphur, lead,selenium, tellurium the steels and therefore the total amount of theageand bismuth in an amount of below 0.3 weight hardenability improvingalloying metals are defined below 0.4 weight below 0.5 weight below 0.3within the range of from 4.5 to 6.5 weight percentages. weight and below0.3 weight respectively.

7. Chromium, molybdenum, tungsten, cobalt, beryl- This invention isillustrated by the following Examlium and boron: ples. I

These metals can be used alone or in combination for Referring to Table1, it shows various kinds of steels improving the ductility and theresistance against the designated by the signs M(or NA-l), NA-2, D, E,softening of the cold workable and age-hardenable NAK-2, NAK-3, N(orNAT-1), NAT-2, A(or NAKT- steel of this invention when less than 2.5weight of l), B, C, NAKT-2, N28, NAKT-3, F, G(or NAK-l), H, chromium,less than 0.5 weight of molybdenum, less I, J, K and L. than 0.5 weightof tungsten, less than 0.5 weight of Table 1 Signs of Compositions ofSteels (76) Steels c Si Mn P Ni Al Cu Ti Others M or NA-l 0.01 I 0.071.20 0.007 0.012 3.65 1.10 0.15

N2 0.009 0.10 1.25 0.010 0.010 3.56 1.04 0.13 Cr 0.50

N3 0.01 0.008 1.19 0.009 0.008 3.52 1.08 0.16 Nb Ta 1 0.08

N5 0.011 0.09 1.21 0.011 0.007 3.40 0.98 0.09 Cr: 0.50,v 0.15

N6 0.008 0.11 1.24 0.013 0.009 3.35 1.01 0.13 c1 1 0.45. Pb 0.15

N7 0.01 0.12 1.17 0.020 0.011 3.60 1.05 0.08 Nb 10.02, Pb 10.15

N8 0.007 0.15 1.23 0.018 0.103 3.55 1.03 0.07 M0 0.2, v 01 D 0.03 0.060.52 0.003 0.019 3.14 0.98 0.90 Be .001

E 0.07 0.15 0.52 0.003 0.008 3.34 0.96 1.04 MO 0.20

N11 0.02 0.13 0.78 0.009 0.012 3.45 1.05 1.01 Nb 1 0.06

NAK-2 0.04 0.10 1.07 0.004 0.090 3.35 1.08 0.98

N13 0.06 0.13 0.65 0.010 0.010 3.10 1.02 0.95 MO 1 0.20. v 0.10

NAK-3 0.03 0.25 0.99 0.008 0.108 3.28 1.12 1.10 MO 0.15, v 0.10

N 01' NAT-l 0.05 0.03 0.70 0.010 0.007 3.85 0.90 0.01 1.05

N18 0.03 0.02 0.65 0.010 0.010 3.64 0.98 0.05 1.15 Mo 10.21

N19 0.01 0.14 0.84 0.008 0.011 3.45 0.97 0.10 1.01 Nb 0.02

N20 0.01 0.12 0.45 0.013 0.016 3.50 1.05 0.05 0.98 Pb: 0.14

N21 0.009 0.09 0.75 0.017 0.018 3.71 1.10 0.13 1.13 Cr 0.45. v 0.10

N22 0.02 0.14 1.12 0.013 0.012 3.49 1.08 0.10 1.15 MO 1 0.12, Pb 0.10

NAT-2 0.03 0.04 1.30 0.015 0.009 3.51 1.02 0.05 1.10 Nb +Ta 0.20

N24 0.02 0.07 1.10 0.013 0.075 3.21 0195 0.11 0.95 B:0.00l.V:0.l0

A0! NAKT-1 0.01 0.08 1.00 0.003 0.008 3.14 0.99 0.90 1.10

NAKT-2 0.02 0.09 1.05 0.003 0.008 3.20 0.95 1.01 1.02 Pb 0.15

Table l-continued Signs of Compositions of Steels (71) Steels C Si Mn PS Ni Al Cu Ti Others N28 0.01 0.11 1.10 0.005 0.102 3.10 0.98 0.97 1.02N29 0.01 0.13 1.25 0.016 0.010 3.25 0.95 1.10 1.12 Mo 0.25. V 0.1 NAKT-30.01 0.11 1.10 0.005 0.102 3.10 0.98 0.97 1.02 Cr 0.87 N31 0.008 0.161.45 0.010 0.095 3.35 1.11 0.98 1.13 V 0.10 N32 0.01 0.13 1.15 0.0170.084 3.10 1.05 0.97 1.03 V 0.10. Cr: 0.56 F 0.05 0.07 1.22 0.003 0.0093.08 1.02 0.87 1.10 G or NAK-l 0.03 0.41 1.53 0.004 0.010 3.27 1.20 1.05H 0.08 0.06 1.70 0.003 0.024 3.14 1.02 0.003 1.06 1 0.07 0.14 0.74 0.0030.009 3.22 1.01 1.00 .1 0.09 0.14 0.50 0.003 0.010 3.22 0.91 1.01 K 0.050.06 1.64 0.005 0.008 3.13 1.16 0.05 L 0.09 0.08 1.50 0.003 0.007 0.060.002 0.98

It should be noted from Table 1 that the steels M, N, A and G are thesame as the steels NA-l, NAT-l, NAKT-l and NAK-l respectively. Also itshould be noted from Table 1 that the steels M (or NA-l NA-2, D, E,NAK-2, NAK-3, N(or NAT-1), NAT-2, A(or NAKT-l), B, C, NAKT-2, N28 andNAKT-3 are the cold workable and age-hardenable steels of this inventionand the steels F, G (or NAK-l H, l, J, K and L are the comparativesteels. Still further, it should be noted that the steels M and NA-2 arethe cold workable and age-hardenable Ni-Al type steels; the steels D, E,NAK-2 and NAK-3 are the cold workable and age-hardenable Ni-Al-Cu typesteels; and steels N(or NAT-1) and NAT-2 are the cold workable andage-hardenable Ni-Al-Ti type steels; and the steels A(or NAKT-l B,

C, NAKT-Z, N28 and NAKT-3 are the cold workable and age-hardenableNi-Al-Cu-Ti type steels of this invention.

Test samples of the steels as shown in Table l were subjected to thesolution treatment at 900C for minutes, followed by cooling them in oiland then the treated test samples were tested for 180 tight-bending andmachinability. Further, the treated test samples were age-treated at525C for 5 hours. The cold workability of the steels which weresubjected to the solution treatment was determined by observing thepresence or the absence of cracks on the bent part of each of the testsamples after they were tested for 180 tightbending in the directionalong the rolling of the steels. The test results are give in Table 2.

Table 2 Signs of Total sum Solution 180 Life of Age- Tensile Steels ofNi, A1 treated tightcutting hardness strength 1 Cu, Ti (7:) hardnessbending tool (in (Vickers) after age- (Vickers) minutes) treated(kg/mm") M or NA-l 4.90 188 good 207 355 118.0 N2 4.73 189 good 356119.5 N3 4.76 190 good 203 359 120.0 NA-2 4.86 179 good 283 360 125.0 NS4.47 193 good 185 371 121.0 N6 4.49 188 good 357 119.0 N7 4.73 191 good265 356 115.3 N8 4.65 192 good 253 361 120.1 N9 5.28 190 good 363 121.0D 5.02 195 good 366 122.0 E 5.34 230 good 350 118.3 N11 5.51 197 good351 117.0 NAK-Z 5.41 195 good 275 380 127.3 N13 5.07 209 good 395 131.7N14 5.20 206 good 394 131.3 N15 5.25 201 good 385 128.0 NAK-3 5.50 225good 258 445 148.7 N or NAT-l 5.81 205 good 141 420 140.0 N18 5.82 210good 415 138.5 N19 5.53 220 good 425 140.1 N20 5.58 207 good 410 136.8N21 6.07 225 good 441 147.0 N22 5.82 218 good 430 143.0 NAT-2 5.68 215good 237 451 154.1 N24 5.22 235 good 455 151.8 A or NAKT-l 6.13 good 180450 155.3 B 5.97 good 490 160.2 C 5.95 175 good 460 153.0 N26 6.52 good467 155.5 N27 6.24 179 good 441 147.0 NAKT-Z 6.18 178 good 270 451 155.7N28 6.07 175 good 260 455 150.1 N29 6.42 182 good 445 148.5 NAKT-3 6.07175 good 260 455 151.0 N31 6.57 184 good 460 153.0 N32 6.15 good 475155.0 F 6.07 180 bad 480 G or NAK-l 5.52 200 bad 360 H 5.22 175 bad 3251 5.23 230 bad 360 1 5.14 335 had 365 K 4.34 175 good 230 L 1.04 150good 180 solution treated hardness of the steels decreases but the 10steels are required to have a very low solution treated hardness forsecuring the reliable 180 tight-bending.

In accordance with this invention, the total sum of theage-hardenability improving alloying metals (Ni,

Al, Cu and Ti) must be kept at the 4.7 weight percentages or more forsecuring the age-hardness equivalent to or of above 300 Vickers hardnessof the cold workable and age-hardenable steel and therefore the solutiontreated hardness of such a cold workable and agehardenable steel can notunlimitedly be reduced by decreasing the total amount of theage-hardenability improving alloying metals. Also the solution treatedhardness of the cold workable and age-hardenable steel of this inventionis required to be kept at 175 Vickers hardness or more for securing theage-hardness of above 300 Vickers hardness. Within the range of such aVickers hardness, the solution treated hardness is not co-related tothe180 tight-bending as shown in Table 2 Referring to FIG. 1, it showsthe relationship between the 180 tight-bending of the test samples andthe amounts of carbon and manganese contained in the test samples.

Referring to FIG. 2, it shows the hardness distribution depending on thedepth measured from the surface of the test sample.

Referring to FIG. 3, it shows four curves 1, 2, 3 and 4 indicating therelationship between the hardness and the depth measured from thesurface of the test samples.

In the FIG. 1, the white marked points indicate that the 180tight-bending of the test samples is good and also the black markedpoints indicate that the 180 tight-bending of the test samples is bad.It is obvious from the FIG. 1 that the 180 tight-bending of the coldworkable and age-hardenable steels of this invention is stronglyco-related to the amounts of carbon and manganese contained in suchsteels and also that it is possible to secure the 180 tight-bending ofsuch steels when they contain less than 0.08 weight of carbon and lessthan 1.8 weight of manganese.

It was also recognized that the use of a suitable amount of themachinability improving alloying metals can improve remarkedly the lifeof the cutting tools without affecting the 180 tight-bending and theagehardness of the cold workable and age-hardenable steels of thisinvention. Still further, it was recognized that the use of a suitableamount of the ductility and temperability improving alloying metals andthe alloying metals for improving the fineness of the crystallineparticles can improve the strength of the cold workable andage-hardenable steels of this invention without affecting the 180tight-bending, the age-hardness and the machinability of such steels.

In the FIG. 2, the test results are shown after the steel A(or NAKT-l)was treated with a liquid nitriding agent, which is sold under the tradename of NI-I-3 by Nisshin Kagaku Kaisha, at 520C for 2 hours.

In the FIG. 3, the curve 1 shows the test results after the steel A(orNAKT-l) was treated at 570C for minutes by using a tufftriding method.The Curves 2 and 3 show the test results after the steel A(or NAKT- lwas treated at 570C for 60 minutes and 30 minutes respectively by usingthe tufftriding method. Also the curve 4 shows the test results afterthe steel G(or NAK- l) was treated at 570C for 180 minutes by using thetufftriding method.

As you can see from the foregoing, it is the critical essential featuresof the cold workable and age-hardenable steel of this invention tocontain less than 0.08 weight of carbon and less than 1.8 weight ofmanganese and to fall within the area as indicated in the FIG. 1. Also,it is the critical essential features of the cold workable andage-hardenable steel of this invention to contain the age-hardenabilityimproving alloying metals in combination of Ni and Al or Ni, Al and Cuor Ni, Al and Ti or Ni, Al, Cu and Ti in which Ni is more than 2.5weight Al is more than 0.6 weight Cu is more than 0.5 weight and Ti ismore than 0.5 weight T, and the total amount of the age-hardenabilityimproving alloying metals is in the range of from 4.5 to 6.5 weightpercentages.

Also the steel A(or NAKT-l) was tested for the 1 80 tight-bending byusing various kinds of the solution treatments and the inventors havefound that the solution treatments have no effect on the 180 tightbending of the steel A. The test results are given in Table 3.

they are fallen within the area enclosed by the line connecting thepoints P, Q and R to the point S, and

Further the steel A(or NAKT-l) was cut into test samples having the sizeof 1 mm thickness X 30 mm Width X mm length and the test samples werebent 9 by the angle of 90 and then the variation of angle was observedafter they were age-treated. It was found that the test samples had alittle strain resulted by the thermal treatments. The test results aregiven in Table 4.

10 neseand said point S indicating zero weight of carbon and zero weightof manganese, and further consisting of as machinability improvingalloying metals, at least one element selected from the group consistingof The test results are compared with much strain of the 5 an effectiveamount up to 0.3 weight of sulphur, an commercial tempered and annealedsteels without effective amount up to 0.4 weight of lead,an-effecshowing the data after they were thermally treated. tive amountup to 0.5 weight of selenium, an effec- Table 4 Bending radiuses(millimeters) Age-treated 0.5 l ,0 l .5

at I. T L T L T L T 500C for -0.o2 0.15 0.08 0.1 1 0.06 0.o4

5 hours 540C for 0.04 0.02 0.04 0,04 0.04 0.01

5 hours 580C for 0.04 ().08 0.04 0.04 0.02 0.02

5 hours Note:

The sign L indicates that the test samples were bent in the directionalong the rolling of the steel A. The sign T indicates that the testsamples were bent in the direction perpendicular to the rolling of thesteel A.

It is obvious from the foregoing that the cold workable andage-hardenable steels of this invention have been developed forobtaining the materials, which are easily workable by pressing,extruding, deep drawing, heading or cutting by applying the coldworkability to the steels under the conditions of the solutiontreatment, having the age-hardness of above 300 Vickers hardness and theimproved machinability after the materials were age-treated. In order toachieve the intended purpose, the specified amount of Ni and Al or Ni,Al and Cu or Ni, Al and Ti or Ni, Al, Cu and Ti is added to the steelsas the age-hardenability improving alloying metals and also the contentsof carbon and manganese are defined as mentioned above for securing thecold workability of the materials. Still further, the ductility andtemperability of the materials, the fineness of the crystallineparticles of the materials and the machinability of the materials areimproved by incorporating the specified amount of chromium, m0-lybdenum, tungsten, cobalt, beryllium and boron as the ductility andtemperability improving alloying metals; the specified amount ofniobium, tantalum, vanadium and zirconium as the fineness improvingalloying metals; and the specified amount of sulphur, lead, selenium,tellurium and bismuth as the machinability improving alloying metalswith the materials. Thus, it is easily understood that the cold workableand age-hardenable steels of this invention can widely be used as thestructural steels having high machinability and less thermal strain andthey are practically useful steels.

What we claim is that:

1. A cold workable and age-hardenable steel, characterized in that itconsists essentially of the weight percentages of carbon and manganesewithin the area enclosed by the line connecting points P, Q and R to thepoint S as shown in the accompanying FIG. 1; an effective amount up to0.6 weight of silicon, and, as age-hardenability improving alloyingmetals, more than 2.5 weight of nickel, more than 0.6 weight ofaluminum, more than 0.5 weight of copper and more than 0.5 weight oftitanium, the total amount of nickel, aluminum, copper and titaniumbeing in the range of from 4.5 to 6.5 weight said point P indicatingzero weight of carbon and 1.8 weight of manganese, said point Qindicating 0.08 weight of carbon and 0.5 weight of manganese, said pointR indicating 0.08 weight of carbon and zero weight of mangative amountup to 0.3 weight. of tellurium and an effective amount up to 0.3 weightof bismuth.

2. A cold workable and age-hardenable steel, characterized in that itconsists essentially of the weight percentages of carbon and manganesewithin the area enclosed by the line connecting points P, Q and R to thepoint S as shown in the accompanying FIG. 1; an

effective amount up to 0.6 weight of silicon, and, as

age-hardenability improving alloying metals, more than 2.5 weight ofnickel, more than 0.6 weight of aluminum, more than 0.5 weight of copperand more than 0.5 weight of titanium, the total amount of nickel,aluminum, copper and titanium being in the range of from 4.5 to 6.5weight said point P indicating zero weight of carbon and 1.8 weight ofmanganese, said point Q indicating 0.08 weight of carbon and 0.5 weightof manganese, said point R indicating 0.08 weight of carbon and zeroweight of manganese and said point S indicating zero weight of carbonand zero weight of manganese, and further consisting of, as ductilityand temperability improving alloying metals, at least one elementselected from the group consisting of an effective amount up to 2.5weight of chromium, an effective amount up to 0.5 weight of molybdenum,an effective amount up to 0.5 weight of tungsten, an effective amount upto 0.5 weight of cobalt, an effective amount up to 0.5 weight ofberyllium and an effective amount up to 0.01 weight of boron, and. asalloying metals for improving the fineness of the crystalline particlesof said steel, at least one element selected from the group consistingof an effective amount up to 0.3 weight of the total amount of niobiumand tantalum, an effective amount up to 0.5 weight of vanadium and aneffective amount up to 0.5 weight of zirconium.

3. A cold workable and age-hardenable steel, characterized in that itconsists essentially of the weight percentages of carbon and manganesewithin the area enclosed by the line connecting points P, Q and R to thepoint S as shown in the accompanying FIG. 1; an effective amount up to0.6 weight of silicon, and, as age-hardenability improving alloyingmetals, more than 2.5 weight of nickel, more than 0.6 weight ofaluminum, more than 0.5 weight of copper and more than 0.5 weight oftitanium, the total amount of nickel, aluminum, copper and titaniumbeing in the range of from 4.5 to 6.5 weight said point P indicat ingzero weight of carbon and 1.8 weight of manganese, said point Qindicating 0.08 weight of carbon and 0.5 weight of manganese, said pointR indicating 0.08 weight of carbon and zero weight of manganese and saidpoint S indicating zero weight of carbon and zero weight of manganese,and further consisting of, as ductility and temperability improvingalloying metals, at least one element selected from the group consistingof an effective amount up to 2.5 weight of chromium, an effective amountup to 0.5 weight of molybdenum, an effective amount up to 0.5 weight oftungsten, an effective amount up to 0.5 weight of cobalt, an effectiveamount up to 0.5 weight of beryllium, an effective amount up to 0.01weight of boron, and as machinability improving alloying metals, atleast one element selected from the group consisting of an effectiveamount up to 0.3 weight of sulphur, an effective amount up to 0.4 weightof lead, an effective amount up to 0.5 weight of selenium, an effectiveamount up to 0.3 weight of tellurium and an effective amount up to 0.3weight of bismuth.

4. A cold workable and age-hardenable steel, characterized in that itconsists essentially of the weight percentages of carbon and manganesewithin the area enclosed by the line connecting points P, Q and R to thepoint S as shown in the accompanying FIG. 1; an effective amount up to0.6 weight of silicon, and, as age-hardenability improving alloyingmetals, more than 2.5 weight of nickel, more than 0.6 weight ofaluminum, more than 0.5 weight of copper and more than 0.5 weight oftitanium, the total amount of nickel, aluminum, copper and titaniumbeing in the range of from 4.5 to 6.5 weight said point P indicatingzero weight of carbon and 1.8 weight of manganese, said point Qindicating 0.08 weight of carbon and 0.5 weight of manganese, said pointR indicating 0.08 weight of carbon and zero weight of manganese and saidpoint S indicating zero weight of carbon and zero weight of manganese,and further consisting of, as machinability improving alloying metals,at least one element selected from the group consisting of an effectiveamount up to 0.3 weight of sulphur, an effective amount up to 0.4 weightof lead, an effective amount up to 0.5 weight of selenium, an effectiveamount up to 0.3 weight of tellurium and an effective amount up to 0.3weight of bismuth, and as alloying metals for improving the fineness ofthe crys- 12 talline particles of said steel, at least one elementselected from the group consisting of an effective amount up to 0.5weight of the total amount of niobium and tantalum, an effective amountup to 0.5 weight of vanadium and an effective amount up to 0.5 weight ofzirconium.

5. A cold workable and age-hardenable steel, characterized in that itconsists essentially of the weight percentages of carbon and manganesewithin the area enclosed by the line connecting points P, Q and R to thepoint S as shown in the accompanying FIG. 1; an effective amount up to0.6 weight of silicon, and, as age-hardenability improving alloyingmetals, more than 2.5 weight of nickel, more than 0.6 weight ofaluminum, more than 0.5 weight of copper and more than 0.5 weight oftitanium, the total amount of nickel, aluminum, copper and titaniumbeingin the range of from 4.5 to 6.5 weight said point P indicating zeroweight of carbon and 1.8 weight of manganese, said point Q indicating0.08 weight of carbon and 0.5 weight of manganese, said point Rindicating 0.08 weight of carbon and zero weight of manganese and saidpoint S indicating zero weight of carbon and zero weight of manganese,and further consisting of, as alloying metals for improving the finenessof the crystalline particles of said steel, at least one elementselected from the group consisting of an effective amount up to 0.5weight of the total amount of niobium and tantalum, an effective amountup to 0.5 weight of vanadium and an effective amount up to 0.5 weight ofzirconium, and, as ductility and temperability improving alloyingmetals, at least one element selected from the group consisting of aneffective amount up to 2.5 weight of chromium, an effective amount up to0.5 weight of molybdenum, an effective amount up to 0.5 weight oftungsten, an effective amount up to 0.5 weight of cobalt, an effectiveamount up to 0.5 weight of beryllium and an efiective amount up to 0.01weight of boron, and further consisting of, as machinability improvingalloying metals, at least one element selected from the group consistingof an effective amount up to 0.3 weight of sulphur, an effective amountup to 0.4 weight of lead, an effective amount up to 0.5 weight ofselenium, an effective amount up to 0.3 weight of tellurium and aneffective amount up to 0.3 weight of bismuth.

1. A COLD WORKABLE AND AGE-HARDENABLE STEEL, CHARACTERIZED IN THAT ITCONSITS ESSENTIALLY OF THE WEIGHT PERCENTAGES OF CARBON AND MANGANESEWITHIN THE AREA ENCLOSED BY THE LINE CONNECTING POINTS P,Q AND R TO THEPOINT S AS SHOWN IN THE ACCOMPANYING FIG. 1; AND EFFECTIVE AMOUNT UP TO0.6 WEIGHT % OF SILICON, AND, AS AGE-HARDENABILITY IMPROVING ALLOYINGMETALS, MORE THAN 2.5 WEIGHT % OF NICKEL, MORE THAN 0.6 WEIGHT % OFALUMINUM, MORE THAN 0.5 WEIGHT % OF COPPER AND MORE THAN0.5 WEIGHT % OFTITANIUM, THE TOTAL AMOUNT OF NICKEL, ALUMINUM, COPPER AND TITANIUMBEING IN THE RANGE OF FROM 4.5 TO 6.5 WEIGHT %, SAID POINT P INDICATINGZERO WEIGHT % OF CARBON AND 1.8 WEIGHT % OF MANGANESE, SAID POINT QINDICATING 0.08 WEIGHT % OF CARBON AND 0.5 WEIGHT % OF MANGANESE, SAIDPOINT R INDICATING 0.08 WEIGHT % OF CARBON AND ZERO WEIGHT % OFMANGANESE AND SAID POINT S INDICATING ZERO WEIGHT % OF CARBON AND ZEROWEIGHT % OF MANGANESE, AND FURTHER CONSISTING OF AS MACHINABILITYIMPROVING ALLOYING METALS, AT LEAST ONE ELEMENT SELECTED FROM THE GROUPCONSISTING OF AN EFFECTIVE AMOUNT UP TO 0.3 WEIGHT % OF SULPHUR, ANEFFECTIVE AMOUNT UP TO 0.4 WEIGHT % OF LEAD, AN EFFECTIVE AMOUNT UP TO0.5 WEIGHT % OF SELENIUM, AN EFFECTIVE AMOUNT UP TO 0.3 WEIGHT % OF
 2. Acold workable and age-hardenable steel, characterized in that itconsists essentially of the weight percentages of carbon and manganesewithin the area enclosed by the line connecting points P, Q and R to thepoint S as shown in the accompanying FIG. 1; an effective amount up to0.6 weight % of silicon, and, as age-hardenability improving alloyingmetals, more thaN 2.5 weight % of nickel, more than 0.6 weight % ofaluminum, more than 0.5 weight % of copper and more than 0.5 weight % oftitanium, the total amount of nickel, aluminum, copper and titaniumbeing in the range of from 4.5 to 6.5 weight %, said point P indicatingzero weight % of carbon and 1.8 weight % of manganese, said point Qindicating 0.08 weight % of carbon and 0.5 weight % of manganese, saidpoint R indicating 0.08 weight % of carbon and zero weight % ofmanganese and said point S indicating zero weight % of carbon and zeroweight % of manganese, and further consisting of, as ductility andtemperability improving alloying metals, at least one element selectedfrom the group consisting of an effective amount up to 2.5 weight % ofchromium, an effective amount up to 0.5 weight % of molybdenum, aneffective amount up to 0.5 weight % of tungsten, an effective amount upto 0.5 weight % of cobalt, an effective amount up to 0.5 weight % ofberyllium and an effective amount up to 0.01 weight % of boron, and asalloying metals for improving the fineness of the crystalline particlesof said steel, at least one element selected from the group consistingof an effective amount up to 0.3 weight % of the total amount of niobiumand tantalum, an effective amount up to 0.5 weight % of vanadium and aneffective amount up to 0.5 weight % of zirconium.
 3. A cold workable andage-hardenable steel, characterized in that it consists essentially ofthe weight percentages of carbon and manganese within the area enclosedby the line connecting points P, Q and R to the point S as shown in theaccompanying FIG. 1; an effective amount up to 0.6 weight % of silicon,and, as age-hardenability improving alloying metals, more than 2.5weight % of nickel, more than 0.6 weight % of aluminum, more than 0.5weight % of copper and more than 0.5 weight % of titanium, the totalamount of nickel, aluminum, copper and titanium being in the range offrom 4.5 to 6.5 weight %, said point P indicating zero weight % ofcarbon and 1.8 weight % of manganese, said point Q indicating 0.08weight % of carbon and 0.5 weight % of manganese, said point Rindicating 0.08 weight % of carbon and zero weight % of manganese andsaid point S indicating zero weight % of carbon and zero weight % ofmanganese, and further consisting of, as ductility and temperabilityimproving alloying metals, at least one element selected from the groupconsisting of an effective amount up to 2.5 weight % of chromium, aneffective amount up to 0.5 weight % of molybdenum, an effective amountup to 0.5 weight % of tungsten, an effective amount up to 0.5 weight %of cobalt, an effective amount up to 0.5 weight % of beryllium, aneffective amount up to 0.01 weight % of boron, and as machinabilityimproving alloying metals, at least one element selected from the groupconsisting of an effective amount up to 0.3 weight % of sulphur, aneffective amount up to 0.4 weight % of lead, an effective amount up to0.5 weight % of selenium, an effective amount up to 0.3 weight % oftellurium and an effective amount up to 0.3 weight % of bismuth.
 4. Acold workable and age-hardenable steel, characterized in that itconsists essentially of the weight percentages of carbon and manganesewithin the area enclosed by the line connecting points P, Q and R to thepoint S as shown in the accompanying FIG. 1; an effective amount up to0.6 weight % of silicon, and, as age-hardenability improving alloyingmetals, more than 2.5 weight % of nickel, more than 0.6 weight % ofaluminum, more than 0.5 weight % of copper and more than 0.5 weight % oftitanium, the total amount of nickel, aluminum, copper and titaniumbeing in the range of from 4.5 to 6.5 weight %, Said point P indicatingzero weight % of carbon and 1.8 weight % of manganese, said point Qindicating 0.08 weight % of carbon and 0.5 weight % of manganese, saidpoint R indicating 0.08 weight % of carbon and zero weight % ofmanganese and said point S indicating zero weight % of carbon and zeroweight % of manganese, and further consisting of, as machinabilityimproving alloying metals, at least one element selected from the groupconsisting of an effective amount up to 0.3 weight % of sulphur, aneffective amount up to 0.4 weight % of lead, an effective amount up to0.5 weight % of selenium, an effective amount up to 0.3 weight % oftellurium and an effective amount up to 0.3 weight % of bismuth, and asalloying metals for improving the fineness of the crystalline particlesof said steel, at least one element selected from the group consistingof an effective amount up to 0.5 weight % of the total amount of niobiumand tantalum, an effective amount up to 0.5 weight % of vanadium and aneffective amount up to 0.5 weight % of zirconium.
 5. A cold workable andage-hardenable steel, characterized in that it consists essentially ofthe weight percentages of carbon and manganese within the area enclosedby the line connecting points P, Q and R to the point S as shown in theaccompanying FIG. 1; an effective amount up to 0.6 weight % of silicon,and, as age-hardenability improving alloying metals, more than 2.5weight % of nickel, more than 0.6 weight % of aluminum, more than 0.5weight % of copper and more than 0.5 weight % of titanium, the totalamount of nickel, aluminum, copper and titanium being in the range offrom 4.5 to 6.5 weight %, said point P indicating zero weight % ofcarbon and 1.8 weight % of manganese, said point Q indicating 0.08weight % of carbon and 0.5 weight % of manganese, said point Rindicating 0.08 weight % of carbon and zero weight % of manganese andsaid point S indicating zero weight % of carbon and zero weight % ofmanganese, and further consisting of, as alloying metals for improvingthe fineness of the crystalline particles of said steel, at least oneelement selected from the group consisting of an effective amount up to0.5 weight % of the total amount of niobium and tantalum, an effectiveamount up to 0.5 weight % of vanadium and an effective amount up to 0.5weight % of zirconium, and, as ductility and temperability improvingalloying metals, at least one element selected from the group consistingof an effective amount up to 2.5 weight % of chromium, an effectiveamount up to 0.5 weight % of molybdenum, an effective amount up to 0.5weight % of tungsten, an effective amount up to 0.5 weight % of cobalt,an effective amount up to 0.5 weight % of beryllium and an effectiveamount up to 0.01 weight % of boron, and further consisting of, asmachinability improving alloying metals, at least one element selectedfrom the group consisting of an effective amount up to 0.3 weight % ofsulphur, an effective amount up to 0.4 weight % of lead, an effectiveamount up to 0.5 weight % of selenium, an effective amount up to 0.3weight % of tellurium and an effective amount up to 0.3 weight % ofbismuth.